("Crazy fire ants" *dying*

)
Okay, so I'll answer the second part and it will help relate to the first..?
No one is born "Talented" or "untalented." The very reason they are called Talents is because the abilities are achieved, they are learned. It's the specific ability by some people to learn something so well and completely, that they pretty much gain a tiny secondary dimension associated with it....like, um, like the difference between watching a movie and watching it in 3D. Sorta. More like "4D" where the theater acts and reacts to the elements on-screen.

(that's a terrible analogy, but maybe it helps.) In any case, this is the theory the characters themselves are working off of, basing their studies around, because it has been the assumed truth.
In the story, it is widely thought that Talents are somehow able to open a sort of "back door" to their mind, a thing that maybe everybody should be able to do but most can't. This "door" of extra-knowldege is accessed by one of two ways, and usually a combination of both: scientific/practical knowledge, and physical/psychological trauma.
So, for example, a scientist working on a lifelong project of oceanology may suddenly be able to create waterfalls out of thin air. But it may only happen after he almost drowns in his bathtub. XD
However, most Talents manifest in younger people, rather than older; often teens and young adults, for a couple reasons: one, because just like with many other things, the younger brain is simply more absorbant to new information and can learn things more quickly and adeptly than someone in their forties. And, two, because...well because hormones. XD Younger people not only have more energy at work in their brains already, but their whole physiology is hard at work growing and maturing and making changes.
This isn't to say that no one has achieved a Talent at old age, but it is far more common for younger people to do so.
On the trauma side of it all, we've all heard of the stories of inhumane strength and abilities in the face of impossible danger. Parents moving vehicles to save children, people surviving falling from extreme heights or beig hit by a bus, the way simple adrenaline can keep a mortally wounded human moving, etc. These types of traumas can be what causes a perosn to snap into having superhuman capabilities.
So, basically, a new talent is "triggered" by one or both of those things.
For the main story, I don't need to have all the answers. As I mentioned, the characters at this point don't even fully understand what's going on with them. That's part of the journey they're on, albiet a somewhat small one. However...um...well not only do /I personally/ want to be able to have an answer for it, but there are sequel ideas, and building on the info of what makes a Talent would be a very great part of those new stories.
